The long-term goals of the proposed research are (1) to continue our attempts to obtain a more comprehensive understanding of the pathogenesis of adverse reactions to injections of x-ray contrast media; (2) based on the foregoing, to refine the assays developed to date to permit a more definitive separation of potential reactors from nonreactors; and (3) based on a better understanding of the pathogenesis of contrast media reactions, we hope to formulate rational plans for therapy of reactions, should they occur.